Metabolomic understanding of the difference between unpruning and pruning cultivation of tea (Camellia sinensis) plants.

Tea (Camellia sinensis) leaf quality depends on several factors such as plucking seasons, cultivation practices, and climatic conditions, which affect the chemical compositions of tea leaves. Pruning has been practiced as one of the common cultivation managements in tea cultivation and is hypothesized to exhibit metabolic differences from unpruned tea plants. Although metabolomics studies provide immense information about production of distinct tea products, the metabolic physiology of the plants cultivated under unpruning conditions is poorly understood. Therefore, in the present study, we explored the metabolic characteristics of tea leaves obtained from unpruned tea plants collected at different plucking seasons in a single year and in a given plucking time in the three successive years, through 1H NMR-based metabolomics approach. Seasonal variations in diverse tea leaf metabolites both in pruned and unpruned tea plants were observed along with marked metabolic differences in tea leaves collected from pruned and unpruned tea plants in a given plucking time. Particularly, in abnormal year of vintage with high rainfall in 2018, high synthesis of glucose followed by high accumulations of catechin, including its derivatives, in unpruned tea, demonstrated intense active photosynthesis compared to pruned tea plants, indicating different metabolic responses of pruned and unpruned tea plants to similar climatic conditions. The current study highlights the important role of tea cultivation practices in tea plants for better management of leaf quality and the strong metabolic dependence on climatic conditions in a given vintage.

Diverse Metabolite Variations in Tea (Camellia sinensis L.) Leaves Grown Under Various Shade Conditions Revisited: A Metabolomics Study.

With the increase of tea (Camellia sinensis) consumption, its chemical or metabolite compositions play a crucial role in the determination of tea quality. In general, metabolite compositions of fresh tea leaves including shoots depend on plucking seasons and tea cultivators. Therefore, choosing a specific plucking time of tea leaves can provide use-specified tea products. Artificial control of tea growing, typically shade treatments, can lead to significant changes of the tea metabolite compositions. However, metabolic characteristics of tea grown under various shade treatment conditions remain unclear. Therefore, the objective of the current study was to explore effects of various shade conditions on metabolite compositions of tea through a 1H NMR-based metabolomics approach. It was noteworthy that the levels of catechins and their derivatives were only influenced at the initial time of shade treatments while most amino acids were upregulated as amounts of shade and periods were increased: that is, the levels of alanine, asparagine, aspartate, isoleucine, threonine, leucine, and valine in fresh tea leaves were conspicuously elevated when shade levels were raised from 90% to 100% and when period of shade treatments was increased by 20 days. Such increased synthesis of amino acids along with large reductions of glucose level reflected carbon starvation under the dark conditions, indicating remarkable proteolysis in the chloroplast of tea leaves. This study provides important information about making amino acid-enhanced tea products based on global characteristics of diverse tea leaf metabolites induced by various shade treatment conditions.

Complete Genome Sequence of Chryseobacterium camelliae Dolsongi-HT1, a Green Tea Isolate with Keratinolytic Activity.

The complete genome sequence of Chryseobacterium camelliae Dolsongi-HT1 is reported here. C. camelliae Dolsongi-HT1, having keratinolytic activity, was isolated from green tea leaves in the Dolsongi tea garden in Jeju, South Korea. The strain Dolsongi-HT1 has 28 candidate protease genes, which may be utilized in further studies and industrial applications of keratinase.

Metabolic phenotyping of various tea (Camellia sinensis L.) cultivars and understanding of their intrinsic metabolism.

Recently, we selected three tea (Camellia sinensis) cultivars that are rich in taste, epigallocatechin-3-O-gallate (EGCG) and epigallocatechin-3-O-(3-O-methyl)-gallate (EGCG3″Me) and then cultivated them through asexual propagation by cutting in the same region. In the present study, proton nuclear magnetic resonance (1H NMR)-based metabolomics was applied to characterize the metabotype and to understand the metabolic mechanism of these tea cultivars including wild type tea. Of the tea leaf metabolite variations, reverse associations of amino acid metabolism with catechin compound metabolism were found in the rich-taste, and EGCG- and EGCG3″Me-rich tea cultivars. Indeed, the metabolism of individual catechin compounds in the EGCG3″Me-rich cultivar differed from those of other tea cultivars. The current study highlights the distinct metabolism of various tea cultivars newly selected for cultivation and the important role of metabolomics in understanding the metabolic mechanism. Thus, comprehensive metabotyping is a useful method to assess and then develop a new plant cultivar.

Synthesis and characterization of novel astragalin galactosides using ß-galactosidase from Bacillus circulans.

Astragalin (kaempferol-3-O-ß-d-glucopyranoside, Ast) is a kind of flavonoid known to have anti-oxidant, anti-HIV, anti-allergic, and anti-inflammatory effects. It has low solubility in water. In this study, novel astragalin galactosides (Ast-Gals) were synthesized using ß-galactosidase from Bacillus circulans and reaction conditions were optimized to increase the conversion yield of astragallin. Purified Ast-Gal1 (11.6% of Ast used, w/w) and Ast-Gal2 (6.7% of Ast used, w/w) were obtained by medium pressure chromatography (MPLC) with silica C18 column and open column packed with Sephadex LH-20. The structures of Ast-Gal1 and Ast-Gal2 were identified by nuclear magnetic resonance (NMR) to be kaempferol-3-O-ß-d-glucopyranosyl-(1→6)-ß-d-galactopyranoside and kaempferol-3-O-ß-d-glucopyranosyl-(1→6)-ß-d-galactopyranosyl-(1→4)-ß-d-galactopyranoside, respectively. The water solubility of Ast, Ast-Gal1, and Ast-Gal2 were 28.2±1.2mg/L, 38,300±3.5mg/L, and 38,800±2.8mg/L, respectively. The SC50 value (the concentration required to scavenge 50% of the ABTS+) of Ast, Ast-Gal1, and Ast-Gal2 were 5.1±1.6µM, 6.5±0.4µM, and 4.9±1.1µM, respectively. The IC50 values (the half maximal inhibitory concentration) of Ast, Ast-Gal1, and Ast-Gal2 against angiotensin converting enzyme (ACE) were 171.0±1.2µM, 186.0µM, and 139.0±0.2µM, respectively.

Functional Properties of Novel Epigallocatechin Gallate Glucosides Synthesized by Using Dextransucrase from Leuconostoc mesenteroides B-1299CB4.

Epigallocatechin gallate (EGCG) is the most abundant catechin found in the leaves of green tea, Camellia sinensis. In this study, novel epigallocatechin gallate-glucocides (EGCG-Gs) were synthesized by using dextransucrase from Leuconostoc mesenteroides B-1299CB4. Response surface methodology was adopted to optimize the conversion of EGCG to EGCG-Gs, resulting in a 91.43% conversion rate of EGCG. Each EGCG-G was purified using a C18 column. Of nine EGCG-Gs identified by nuclear magnetic resonance analysis, five EGCG-Gs (2 and 4-7) were novel compounds with yields of 2.2-22.6%. The water solubility of the five novel compounds ranged from 229.7 to 1878.5 mM. The 5'-OH group of EGCG-Gs expressed higher antioxidant activities than the 4'-OH group of EGCG-Gs. Furthermore, glucosylation at 7-OH group of EGCG-Gs was found to be responsible for maintaining tyrosinase inhibitory activity and increasing browning-resistant activities.

Identification of Oligosaccharides in Human Milk Bound onto the Toxin A Carbohydrate Binding Site of Clostridium difficile.

The oligosaccharides in human milk constitute a major innate immunological mechanism by which breastfed infants gain protection against infectious diarrhea. Clostridium difficile is the most important cause of nosocomial diarrhea, and the C-terminus of toxin A with its carbohydrate binding site, TcdA-f2, demonstrates specific abolishment of cytotoxicity and receptor binding activity upon diethylpyrocarbonate modification of the histidine residues in TcdA. TcdA-f2 was cloned and expressed in E. coli BL21 (DE3). A human milk oligosaccharide (HMO) mixture displayed binding with TcdA-f2 at 38.2 respond units (RU) at the concentration of 20 µg/ml, whereas the eight purified HMOs showed binding with the carbohydrate binding site of TcdA-f2 at 3.3 to 14 RU depending on their structures via a surface plasma resonance biosensor. Among them, Lacto-N-fucopentaose V (LNFPV) and Lacto-N-neohexaose (LNnH) demonstrated tight binding to TcdA-f2 with docking energy of -9.48 kcal/mol and -12.81 kcal/mol, respectively. It displayed numerous hydrogen bonding and hydrophobic interactions with amino acid residues of TcdA-f2.